Concentrators of telephone lines or the like



JUIY 5, 1960 A. J. HENQUET ET AL 2,944,115

coNcENTRAToRs oF TELEPHONE LINES 0R THE LIKE Filed sept. 27, 1957 l2 Sheets-Sheet l l2 Sheets-Sheet 2 A`. .1. HENQUx-:T ET AL CONCENTRATORS OF TELEPHONE LINES OR THE LIKE Attorney July 5, 1960 Filed sept. 27, 195'? 12 Sheets-Sheet 3 A. J. HENQUET ET AL CONCENTRATORS OF TELEPHONE LINES OR THE LIKE July 5, 1960 Filed sept. 27, 195',7

n .ma

A. J. HENQuE-r ET AL 2,944,115

coNcENTRAToRs 0F TELEPHONE LINES 0R THE LIKE July 5, 1960 l2 Sheets-Sheet 4 Filed Sept. 27. 1957 frfzazaas44ss wjf .ffl XxX/ ff/X .Wi

uw wf uly 5, 1960 A. J. HENQUET ET AL CONCENTRATORS OF TELEPHONE LINES OR THE LIKE Filed Sept. 27. 1957 l2 Sheets-Sheet 5 Y nuenlor A. J. Henue J. J., 'Devrait BWM/4 ttornev 'JUHY 5, 1960 A. J. HENQuE-r ET AL 2,944,M5

coNcENTRAToRs oF TELEPHONE LINES 0R THE LIKE Filed Sept. 27, 1957 12 SheeS-Sheet 6 Attorney July 5, 1960 A. J. HENQUET ETAL 2,944,315

coNcENTRAToRs oF TELEPHONE LINES 0R THE LIKE:

Filed Sept. 27, 1957' l2 Sheets-Sheet 7 n N" 'ubu Inventor A Horn e y 31133 5 1950 A. J. HENQUl-:T ET AL 2,944,115

CONCENTRATORS OF TELEPHONE LINES OR THE LIKE Filed sepi. 27, 1957 12 Sheets-Sheet 8 V sly! Inventor A-J. Henquei- J. J. 'perro-c Atlorney July 5, i960 A. J. HENQUET r-:T AL ,944,135

coNcENTRAToRs oF TELEPHONE LINES 0R THE LIKE Filed sept. 27, 1957 12 Sheets-Sheet 9 BWM/1 A Homey Juy 5, 1960 A. J. HENQUET ET AL 2,9%15

CONCENTRATORS OF' TELEPHONE LINES OR THE LIKE Filed sept. 27. 1957 12 sheets-sheet 1o dk a? nvenlor A. J. Hencwel: J. Jfperrot BMWA A Harney July 5, 1960 A. J. HENQUET ET AL 2,944,115

coNcENTRAToRs oF TELEPHONE LINES 0R THE Lm:

Filed Sept. 27, 1957 l2 Sheets-Sheet 11 l 2 $5173 sa 134 Inventor A.J. Henqfe J. J. perra A ttorne y July 5, 1960 A. J. HENQUET ET AL 2,944,115

CONCENTRATORS OF' TELEPHONE LINES OR THE LIKE Filed Sept. 27. 1957 12 Sheets-Sheet 12 FlgA .1.4 l l u ,Hals 1.4 VA m A'a A la j 'b's X ZIP A b A 'L' f., c A c inw Inventor A.J. Henquet J.J.'Per\^ot Attorney .nu if l Patented July s l 960 CONCENTRATORS OF TELEPHONE LINES OR THE LIKE Andr Jean Henquet and Jean Jacques Perrot, Boulogne- Billancourt, France, assignors to International Standard Electric Corporation, New York, N.Y., a corporation of Delaware Filed Sept. 27, 1957, Ser. No. 686,662

Claims priority, application France Sept. 28, 1956 7 Claims. (Cl. 179-48) This invention refers to concentrators of telephone lines or the like, that is, automatic equipments that in the case of telephone systems allow handling a local subscriber group through a smallnumber of telephone lines outgoing from the exchange.

These equipments diier from similar so-called building satellites in that they serve larger subscriber groups, through a telephone-line multipling group, with switching means that allow seizing any free line. They compriseV a set Anear the subscribers, which concentrates the Wires (interior or at any rate relatively short) of these subscribers on this multipling group, and a set B, which concentrates the same subscribers on the same multipling group at the exchange. It is particularly a question of outgoing positions on the line finders, used to ring the concentrated subscribers. The incoming positions of these subscribers are further `alike in numerous systems as regards the routing of incoming calls, but calling subscribers must nevertheless be identified in order to busy their outgoing positions and operate their meters. It is therefore also a question of concentrating the incoming positions, or at least their control wires (busying and metering).

The concentrator equipments comprise a control device capable of seizing one out of a plurality of incoming or outgoing calls originating at the same time, of seizing a free trunk and of connecting to this trunk (l) the Wire of the particular calling or called subscriber involved and (2) that subscribers'position at the exchange. The problem that arises in the concentrators is primarily to provide a dependable control device, as simple as l possible and employing few connecting Wires between the two sets, because thes-e wires are taken from the telephone-line multipling group and accordingly reduce the number of lines that can serve as trunks for the connections. Moreover, it is desirable that distant set A not comprise an individual supply source but that it be supplied by the exchange, also by means of Wires from the same multipling group.

The object of this invention is particularly to provide means and arrangements of means that will allow designing a control device capable of Ameeting all these requirements and of being used in similar applications. The invention refers particularly to concentrators using cross-bar switches, the horizontal multiples (selecting bars) of which carry the wires or the positions of the subscribers, while their vertical multiples (selectors) carry the trunks. These latter can be used in both directions in certain arrangements or else, in other arrangements, be assigned partly to incoming calls and partly to outgoing calls.

An arrangement in accordance with the invention comprises, in each set, a test device sensitive alike to the incoming calls of all the subscribers and to the outgoing oalls to all the subscribers and capable of holding a single call and of identifying the calling or called subscriber in code form, with means for signaling to set B the existence of a call; in set B, an option device, receiving the ringing signals from the two test devices and capable of choosing an outgoing call in order to handle it; a code-sending device, of the remote-controlling and remote-controlled type, with set B as the controlling station and set A as the controlled station, capable as regards incoming calls of recognizing the code set up in set A and of registering it in set B and, fior outgoing calls, of sending to set A, in order to have it registered there, the code set up in set B; in each set, a selecting device the positioning of which represents the registering of the code sent; in each set, a connecting device controlled by the sets selecting device to bring about the connection to a trunk, by the sets crossbar switch, of the wire and the position of the subscriber identiied by thecoding and selecting devices, the connecting device of set B comprising means for first seizing a free trunk and the connecting device of set A being controlled partly by set B and partly by the trunk seized; and means for isolating the wire and the position of the particular subscriber involved from the respective test devices following their connection.

The arrangements in accordance with the invention particularly use a known test device, made up o-f a series of relay and rectifier matrices. one call at a .time and neutralizes the others. It identities the subscribers in the form of multi-element code combinations. For example, for 52 subscribers, a first 4-element matrix defines a 13-subscriber group by means of each element and two other 5- or 6-elen1ent matrices identify one subscriber among 13 by means of combinations comprising 2 elements out of 6.

In an arrangement in accordance with the invention, the code sent can be registered each time in both sets by positioning the two selecting devices in accordance with the code set up in the calling set (that is, the set whose call is handled).

The code-sending device particularly uses synchronizedstepping switching means in both sets, controlled by pulses emitted by set B. In accordance with another feature of the invention, the sending device further comprises a code-sending loop, controlled in both sets by the synchronized stepping and showing in each set two paths, one of which is further controlled by the code set up in that set. This loop, closed in set A, is supplied by set B in one direction or the other in passing, in the calling set, over the path controlled by the code set up in that set and over the other path in the other set, so that each selecting device is positioned in accordance with the code formed in the calling set, by pulses whose existence is revealed by that code and whose moment is revealed by the synchronized stepping.

Preferably, the identiication or coding devices (comprised in the test devices) and the selecting devices consist of similar relay groups, so that each relay of the coding device positions its corresponding relay in the selecting device through the sending loop.

For the synchronized-stepping switching the arrangements in accordance with the invention particularly employ a known metering-relay chain, controlled by alternate pulses (positive and negative). v

In accordance with another feature of the invention, the signal revealing the existence of an incoming call is sent by set A through the closing of a third path of the sending loop in that set and is also received over a third path in set B, whose control device is in normal position. The supplying of this loop in normal position is reversed in set B by the existence of an outgoing call (this constituting the signal revealing such existence) and This device holds only the current then flows, inset A, over a fourth path, which is independent of the existence of an incoming call. The paths here mentioned are preferably controlled by the normal condition of various devices coming into play in a connection operation, particularly synchronized-stepping relays and selecting bars in crossbar switches.

In accordance with another feature of the invention, the option device comprises a ringing relay, operated by the ringing signal of one set or the other, and two option relays, selectively operated by the ringing relay, the one when there is an outgoing call, in order to handle it (in preference to an incoming call), and the other when there is no outgoing call, in order then to handle an incoming call.

The invention provides arrangements for the particular case where the concentration involves the terminal positions of the subscribers at an exchange where the concentrated subscribers are normally equipped with line circuits and positions on the call iinders as also on the line finders. It also provides for the case where the concentration involves only the outgoing positions of the subscribers (on the line finders) with, as regards incoming'calls, only the control wires (busying and metering) of the incoming positions. In these latter arrangements, part of the trunks are preferably assigned to outgoing calls, with concentration on these trunks of the outgoing positions, and another part of them is assigned to incoming calls, with extension of these trunks from there to the second ca ll iinders but with concentration on them of the control wires (busying and metering) associated with the positions on the line nders. The exchange equipment of concentrated subscribers is then reduced through elimination of the line circuits and the first call finders. On'the other hand, the equipment of set B is then supplemented in order to ensure the proper operation of the line finders and of the second iinders.

In accordance with another feature out of the invention, the supplying of set A by set B is done by means of alternating current superimposed on the connecting wires of the control device and rectiiied in set A. A supply loop is provided particularly through the use in one direction of the two wires used for sending the synchronized-stepping pulses and through the use in the other direction of the two wires of the code-sending loop.

The driving of the crossbar switches can be done in a manner known for switches connected together through their vertical multiples. It is done under the control of the respective selecting devices, starting with the switch of set B, upon the reception of the code.` This operation comprises the testing and the seizure of a free trunk. The switch of set A is controlled with the aid of the trunk seized, without supplementary connecting wires.

Other features and advantages of this invention will become apparent from the following description of embodiment examples with reference to the accompanying drawing, wherein:

Fig. l shows schematically a concentrator arrangement in accordance with the invention, with connection to the terminal positions.

Fig. 2 shows schematically another arrangement in the same case. y

Fig. 3 shows schematically another arrangement, with connection to the second call finders.

Fig. 4 shows a matrix testing device for the calls.

Fig. 5 shows the synchronized-stepping and code-sending `chains in set A.

Fig. -6 shows the corresponding chains of set B, the option relays and a few auxiliary relays.

Fig. 7 shows the pulse-rate device provided in set B.

Fig. 8 shows the trunk-testing device provided in set B.

Fig. 9 shows the switch equipment, its connections and its selector and selecting-bar magnets in set A.

Fig. l0 shows the corresponding equipment in set B.

Fig. 1l shows the assumed equipment of a line circuit at the exchange, connected to set B.

in Fig. 4, with a few changes for a variant of the circuits.

Fig. 13 shows a variant of the chains shown in Fig. 5.

Fig. 14 shows a corresponding variant of the chains and relays shown in Fig. `6.

Fig. l5 shows a corresponding variant of the equipment of the selecting-bar magnets in set A, shown at the bottom of Fig. 9. t

Fig. 16 shows a corresponding variant of the equip` ment of set B, shown at the bottom of Fig. li).

Fig. 17 shows a trunk-testing device similar to the one shown in Fig. 8, intended for another variant, where the subscribers do not have incoming positions at the exchange and the trunks are assigned to the calls, either incoming or outgoing.

Fig. 18 shows the corresponding equipment of the switch, its connections and its selector magnets in set B, similar to the top portion of Fig. 10.

Fig. 19 shows the assumed equipment of an incoming position, with the meter.

Fig. 20 shows theV assumed equipment of an incoming trunk, replacing a first iinder circuit vis-a-vis the exchanges second iinders. Y

The concentrator installation shown in Fig. 1 connects fifty subscribersl to their terminal positions at Vthe exchange by means for example of 8 telephone lines used as Itwo-way trunks. In each concentrator a crossbar switch provides the necessary switching between the subscribers wires or positions, connected to its horizontal multiples, and the trunks, connected to its vertical multiples. The operations whereby a calling or called subscriber is connected to his position at the exchange are controlled by a control device whose functions and component devices will be described later.

In both sets, A and B, each subscriber line is connected, by individual cut-off means, to a test and identitication device. 'This device tests all vcalls occurring and Vconrms the testing of one of these calls, which is thus held. The relays or other means of confirmation identify the held call in code form, that is, they code the call. The existence of a held call, regardless of its nature, is signaled by the two devices to `an option device comprised in set B and that chooses the call to be handled, as between an incoming call signaled by set A and an outgoing call signaled by set B. 'It will be seen later on that the call signals are controlled by the normal position of a series of components of the control device, as also of the selecting bars of the crossbar switches. Consequently, as soon as the option device begins a connection operation, it is cut oif from call signals for the duration of that operation.

The option device starts a code-sending device. The latter must position, in accordance with the code set up in the calling set, selecting devices that will control, each in its own set, the driving of the bars of the crossbar switches. In the variant here shown, each set comprises a selecting device that can be positioned either as required by the call-coding device of that same set, when that set is the one whose call is handled, or as required by the coding device of the other set, in the opposite case. The code sent from one set is therefore registered in both sets by the positioning of their selecting devices.

The sending device comprises, in each set, a synchronized-stepping switching device operated by pulses sent from set B and a coding device for the oall handled, which registers the code sent either from the same set or from the other and which constitutes said selecting device.

It will be assumed rst that an incoming call A is handled. The option device starts the pulsing device, which causes the synchronized stepping of the switching devices in both sets, so as to dene consecutive moments. At the same time, the option device feeds a codesending loop in direction A. Still in direction A, this loop continues over a connecting wire to set A, where it crosses the synchronized-stepping device and takes' a path that` then crosses the incoming-call coding device, which is a routing positioned with the identification coding (sic Translator). The loop thereupon passes into the coding device of the call handled, returns over a connecting wire to set B and passes into the coding device of this set. From this device it takes a path that leads directly to the synchronized-stepping device of set B. The loop crosses this device and returns to the option device. It will be understood that [in the stepping, code and coding devices the loop comprises a series of branches, one for each moment. There is for each moment a relay or `other receiving element in the coding device. In set A,

these branches are controlled, the stepping aside, by the code device. In both sets, the corresponding relays or other coding elements are switched in at the same moments by the respective synchronized devices. The corresponding relays `are operated at `the moments determined by the code device of set A, operation constituting the coding of the call handled. It will be seen later on that the handled-call code is the same or about the same as the identied-call code, so that the control of the handled-call coding device by that of an identilied call can be done by simple means.

If it is assumed now that an outgoing call is handled, the option device feeds the code-sending loop in the other direction B. The loop then takes in set B a path passing through the outgoing-call code set up by the identification device and in set A a path leading directly from the handled-call coding device to the synchronized device, without passing through an incoming-call code. The two handled-call coding devices are thus positioned in accordance with the code of the outgoing call that is handled in this case. l

After the code sending, a connecting device is started in set B (by the ending of the synchronized stepping). It is a question of a device known in principle, ,which is ad-apted to its application to the concentrator particularly by the fact that the selecting device controlling the choice of a selecting bar consists of the code dev-ice positioned by the handled-call coding device, such as a routing switch formed by the contacts of the coding relays.` The connecting device tests the trunks in order to seize a free trunk and drives the switch, namely, rst the selecting bars, under the control of the handled-call code, and then the selector of the seized trunk.

For the trunk, the connecting device of set B starts the connecting device of set A, which has only a connecting function, namely, the driving of the selecting bars under the control of the handled-call code and then of the selector ofthe calling trlmk.

The cut-oit devices are then operated in both sets in order to cut the line olf from the test devices. Further, certain secondary operations are performed for the transfer of the subscribers loop and of its supply.

The control device then homes and is ready to handle another call. The switch selectors and the cut-oli:` relays release at the end of the call.

In another arrangement in accordance with the invention the identication devices are used as selecting devices. Upon the sending of the code from the calling set to the other, the code set up by the calling sets identication device is registered by the other sets identification device. Particularly, in a variant of the abovementioned sending device, this other sets identiiication device is positioned by pulses flowing into the code-sending loop under the control of the calling sets identitication device.

Fig. 2 shows the above arrangement. The general layout and `the test and identiiication devices, as Well as the option device, are in principle the same as in Fig. l. However, the option device signals its choice to the sets, particularly to set A, that an outgoing call is going to be handled and to set B that an incoming call is going to be handled, as the case may be. The sending of an incoming-call signal to set B poses no problem'. The sending of an outgoing-call signal to set A calls for a supplementary connection between the sets, which must be provided Without adding wires. For this purpose, use can be made for example of the fourth path, mentioned above, of the sending loop in set A, which the option device supplies in the case of an outgoing call. This path can comprise a relay or other device operated in this case, such operation representing the desired signal. Or else use can be made of the synchronized-stepping device, when it is driven by pulses of alternate signs, as mentioned above. Assuming that the iirst stepping pulse is positive, it can be made, in the case of an outgoing call, to come after a negative pulse, which will not aiect the synchronized-stepping device and which will represent the desired signal.

The' sending device comprises the same synchronizedswitching device and, as has been shown, uses the other sets identification-coding device to register in that other device the code sent 'from the calling set. In the abovementioned test device it has been seen that the call held neutralized all other existing calls. In this device, any call positively held would neutralize all other calls. The registering of the code sent in this arrangement can be effected `by applying the code signals as a fictitious call from the subscriber held in the calling set to the test device of the other set. This test device then identities that call on its own coding device, replacing it, if necessary, With a previously-held actual call. Particularly, the code pulses, controlled in the calling set by the stepping and coding devices of this set, can operate in the other set a relay supplying local pulses, controlled by this other sets stepping device lin order to be applied to the corresponding inputs of the test device.

It will be assumed iirst that an incoming call A is handled. The option device sends set B an incomingcall signal and starts the pulsing device and, through this device, the two stepping devices. At the same time, the option device feeds the code-sending loop in direction A. Still in direction A, this loop, after having reached set A and having crossed its stepping device, takes a path that crosses the incoming-call coding device and returns directly (over a common Wire) to set B. In this set, the loop takes a path that leads to the coding device, then it crosses the stepping device and returns at its other end to the option device feeding it. The coding device of set B, which is normally positioned to identify a held call present in set B, is now positioned in accordance with a held call present in set A, which is then handled. In the case of a local-pulse relay, the loops return path A in set B can comprise this relay, instead of going to the coding device, and the pulses of this relay can cross the stepping device and then go to the coding device. Further, other equivalent circuits can be provided for the sending loop, in this arrangement as in that shown in Fig. 1 and in other arrangements in accordance with the invention. For example, in the case of direction A, the sending loop can cross the stepping device at the output of set A and at the input of set B, instead of the input of set A and of the tinal portion of the loop in set B, as shown in Figs. l and 2.

If it is now assumed that an outgoing call is handled, the option device sends an outgoing-call signal to set A and feeds the code-sending loop in the other direction B. It is then the coding device of set A that is positioned in accordance with that of set B.

After the code sending, the connection operations are performed as in the arrangement of Fig. l, it being understood that the selecting device that controls the driving of the crossbar switch is a code device associated with the same coding device as the code device that controls the code sending (switchings set up by two contact groups of the same relay set).

The installation shown in Fig. 3 connects the subscribers to their outgoing positions at the exchange. For

7 incoming calls, the trunks are extended directly to the second call.. finders. The subscribers do not have incoming positions properly so called (wires frz-W) butwhen o second vgroupof 13 magnets, in. accordance with the following table: f

there is an incoming call the subscriber is connected to Group Mugs Bars lvmgnts Dividingthe (busy and metering) control wires `associated with v Magnet his outgoing position.A The trunks are here assigned in part to incoming and in part to outgoing calls. l llzl The connecting device that comes into play after the 27 39 1 13 .1 13 '2 code sending is partly in duplicate. Depending upon t0-52 1-13 Y 142.5 2 whether the call handled is an incoming or an outgoing i call, it must seize a trunk belonging to one group or the Each line is connected in normal position, with a cutother. Set B therefore comprises a dual trunk-testing off device whose `details will be given later, to atest device, Whose portion A or portion B comes into play Wire'multipled tothree matrices, with decoupling rectidepending upon the type of call, incoming or outgoing, tiers. In Fig.4 itis assumed that this is line No. 17, that that the option device has chosen'to handle. The con- 15 is, the No. .4 line in group 2. The iirst matrixAhas necting means, likewise in duplicate, act upon the correfour inputs, each ,input being multipled to 'thef13` test spending selectors of the switch of set B and drive the wires of thej corresponding group. This matrix identities connecting device of set A over the corresponding trunks. the four groups by means of four relays, one for each The connecting device of set A also drives two selector group. 1. Y Y l sets but without making any distinction between them, The -deutication of the 13 linesV of. any' group yis because its operation no longer depends, as is the preeffected by `two other matrices, namely, 5input matrix B ceding arrangements, upon the type of call handled. The and 6-iI1put matrix Ci by means 0f SX relays, tW0 for driving of the selecting bars, which in each set precedes each line, in accordance with the following table:Y

Line 1 12 l 1g 1g 5 i 1 2 Relay positioned by (B) Relay positioned by (C) the driving of the selectors and which is controlled by the selection code positioned in that set, does not depend upon the type `of call handled, in one set or the other.

The connection of an outgoing call in set B entails the connection of a .piece of equipment to the control wires of the outgoing position, vfor example the connection of a holding relay to the c Wire. The connection of an incoming call also entails'the connection of a piece of equipment to the control wires leading to the second nders and, moreover, a strapping between these wires and those of the calling-subscribers outgoing position, in order to busy that position and have access to the meter. It will be understood that in the absence of incoming positions the meters will be associated with the outgoing positions, even if they are used for incoming calls. At lany rate, cut-oit means are provided, as in the preceding arrangements, to cut the connected-subscribers position or wire from the call-test device in both sets.

In all these arrangements, suitable connecting devices, not shown in Figs. l to 3, such as contacts, temporary loops vand supply bridges, etc., can be inserted at suitable points of the trunks to provide for any necessary gating, so as to extend the connections under proper conditions.

A variant (Figs. 4 to 11) will be described below as an embodiment example of Fig. l.

A call test `and identification device is shown in Fig. 4. It is adapted to the make-up of crossbar switches of the type whose use is contemplated in this embodiment example. Switches of this type comprise 13 selecting bars capable of being placed in one direction or the other by means of 13 2=26 magnets. A 14th bar is used for dividing, different connections being established depending upon whether it lis placed in one `direction or the other by means of its 2 magnets. Thus are obtained 13 2 2=52 different connections.' The selectors will be assumed to be 8 in number, so that a multiplying group of 8 trunks will be available between concentrators A and B.

The present embodiment example uses the full capacity of these switches and allows connecting up to 52 lines. These lines are divided'i-nto 4 groups of 13. Groups l and 2 are connected in one position of the dividing bar, and groups 3 and 4 in the other. Groups 1 and 3 are connected by placing the 13 bars in one direction by means of the rst group of 13 magnets and groups 2 and 4by placing themin theY other direction by means of the In normal position, test relays aa of matrix A are supplied, forexample by a ground if the line wires used for the test are connected to the battery, or vice versa. It will be assumed that lines 4, 1'7, 18 and 39 are calling. Relays za-1, 2, 3 energize. Relay cra-1 applies a ground to a cross wire `,rnultipled to the corresponding identification relay aband to the other three test Wires. Relays aLl-,2, 3 operate similarly and al-l the relays aa fle-energize, thenoperate again, etc. One ofthe relays -ends up by holding and keeps the others unoperated. It -will be assumed that this is relay `azz-2, Corresponding to lines 17 and 18. The corresponding relay rzb-2 is'operated.

Y Matrix B is supplied by a contact of relays zb-L14 and is therefore now supplied by the contact of relay zb-2. The test wires of groups 1, 3 and 4 have been grounded by matrix A. Wires 17 and 18, that is, No. 4 and 5 of group 2, `are connected to the second input of matrix B and cause the operation of relays ,ac-2 and rrd-2. Relay ac-Z applies a ground to the other four inputsof the matrix.

Matrix C is supplied by a contact of relays ad-l-S and is therefore now supplied ,by the contact of relay crd-,2. Wires No. 4 and 5 of all the groups are respectively connected to the third and Vfourth inputs of matrix C. Relays ze-3 4 operate, cause each other to release,

etc. It Willbe assumed .that relay 1e-3 holds. Relay :zd-3 operates. The combination zb-2, ad-2, 3 identities line 17.

If the test supp-ly is :in the opposite direction, as is the case for outgoing calls, where the test is on the c Wire grounded by the call, the matrices are supplied by batteries (test relays and identication relays) and the rectiers are connected in the opposite direction.

Referring to Fig. 5, the sending device in set A comprises a synchronized-stepping chain, connected to set B by a two-wire line trl-tb, and a code-sending chain, also connected to set B by a two-Wire line tid-tb.

The stepping chain compirses four relays af--d, corresponding to identiication relays ab-1-4 of Fig. 4; six relays ah-l6, corresponding to relays azi-1 6, `and one supervisory relay aj. It comprises two paths: `the wrst is for the positive pulses and uses wire ta, rectifier R1, contact chain 51, the relays and return wire 52,l connected `directly to wire tb; the second is for the negative pulses and uses wires rb and 512, the relays, contact chain v53, rectifier R2 and wire ra.

`a parity, upon locking,

9 'The sending chain comprises `'four relays zg-1 4, cor'- responding to relays ab and af (with a translation, however, as will be explained later), and six relays ai, corresponding to relays ad and ah. It also comprises tWO paths: the first is for the positive supply (incoming calls) and uses wire 2a', rectifier R3, contact chain 54, the relays lin passing through the front contacts of the corresponding identification relays, return `wire 55, rectifier R4 and wire tb; the second is for the negative supply (outgoing calls) and uses wire tb; rectifier R5, contact chain 56, the relays, return wire SS, rectifier R6 and wire ta. Further, a third path is set up lat the end of the firstV by a shunt controlled in parallel 'by the front contacts of relays arl-l-S land then in series by the back contacts of selecting-bar magnets SS-ll-26 and of dividing-bar magnets SX-l-Zg and la fourth path is set up at the end of the second, passing through the final portion of the third, controlled only by the back contacts of the magnets.

The sending line `is supplied continuously in the positive direction (arrow A) in readiness for an incoming call. When an incoming cal-l is identified the loop iS closed over the third path: wire ta', rectifier R3, chain 54,` back aj, al1-6 1, olf-44, front of one o-f relays ad-1-5 in matrix B (Fig. 4), back of magnets SX-l-Z and SS-1-26, return wire 5S, rectifier R4, wire tb. This loop constitutes the incoming-call signal sent by set A to set B.

As la result of that signal, set B holds thepositive feeding of the sending line `and sends eleven stepping pulses, alternately positive and negative, to line taz-tb. The first pulse (positive) operates relay alf-'1: Wire ta, rectifier Rl, chain l (back contacts of relays 11h-6, 4, 2, tf-4, 2), af(l)-.`i, return wire 52, wire ib. Over a front Contact, relay af-i applies a ground to locking wire 57 `and holds on this ground: ground, -af-l, Wire 57, r-rzj, af(ll)*.l, battery. The second pulse (negative) operates relay lf-2; wire Ib, wire S2, af(I)-2, :La-1, chain 53 (back contacts of relays tlf-3, zh-1, 3, 5), rectifier R2, wire la. The third pulse (again positive) will operate relay 1f-3 over t-af2, etc. The last (also positive) will operate relay ai over t-nh6.

The even relays are locked over wire 57 by lockingcontact chain 5S. The odd relays are locked over Wire 57 by locking-contact chain 59 and r-aj. Each relay of cuts off the rest of the locking chain and causes the preceding relay of the same parity to fall back. When finally relay aj operates, it doubles the ground on Iwire 57 and breaks the locking chain of the odd relays, `as also the locking of relay afi-1. Relay 41h-6 holds over its locking winding, and relay ai is held by the current that set B sends to line ta-zb without changing sign, up till the end of the connection.

The operation of each relay of the stepping chain switches contact chain 54 to the corresponding relay of i the `sending chain. Owing to the identification, one of relays ab and two of relays ad are operated, namely, zb-2 and zd-2, 3 in the above-described example. Were there no translation, `relay 1g-2 would operate over l-af-Z, t-ab-Z upon the operation of relay af-Z. The translation lbetween the identification code (relays alb-1 4) and the selection code (relays zg-L4) is as follows:

For this translation, relays ag-1-4 are controlled by relays al1-1 4 as follows:

ag-l by t-ab-L 2; ag-Z by t-ab-3, 4 tlg-3 by t-ab-l, 3; :zg-4 by l-ab-Z, 4

Relay ag-l is therefore operated upon the operation of relay af-l by t-af-I, l-ab-2, and relay 1g-4 is operated upon the operation of relay 1f-4 by t-af-4, Lab-2. Thereupon, relay zi-2 is operated upon the operation of relay ah-Z by t-ah-Z, t-ad-Z, and relay :zi-3 is Voperated upon the operation of relay afl-3 by t-ah-S, t-ad-S.

Selecting relays ag and ai are locked over their locking winding and their locking contact on locking wire 57 up till the end of the connection.

The operating current of each selecting relay, which lasts from the operation of the corresponding stepping relay up to the operation of the next stepping relay, is a pulse whose moment is dened by the stepping pulse, something that allows the equipment of set B to determine which selecting relays have operated in set A and consequently the identity of the calling line. It will be seen later on that this `determination is effected very simply, by means of two chains similar to the ones contained in set A.

After the operation of relay aj, line ta'tb is directed by this relay to a fifth path, consisting of a chain 60 comprising front contacts associated with selectingbar magnets SS-1-26 and SSX-1 2, 1front contacts am`1-,8 corresponding to the selector magnets, and, in series with each of these latter contacts, back contacts V-l-S `associated with these magnets. This fifth path is closed after the positioning of the selecting bars and relays am, which prepare the selectors, making sure that the corresponding selector is actually in nonnal position. The `closing of this loop represents ya signal for set B, which then operates the prepared selector.

In the case of an outgoing call, set B reverses the feeding of sending line tatb. This latter then shows a loop over the -fourth path, which does not depend on an incoming call: wire tb', rectifier R5, chain 56 (r-aj, r-ah-6-1, raf-4-1), r-SX-ll-2, r-SS-1-26, return wire 55, R6, wire ta. This loop checks only that the selecting bars are actually in home position. Set B does not maintain the negative feeding of line ta'tb' but sends stepping pulses as in the case of an incoming call and sends (negative) pulses over the sending line at moments defining the called-lines selection code. Thus, to ring line 17, code pulses are sent at moments 1, 4, 6 and 7, that is, upon the operation of relays tlf-1, 4 and zh-2 3. Over chain 56, these pulses operate the corresponding relays ag-1, 4 and ari-2, 3, which lock las before. After the operation of relay ai, the same fifth path appears over the :sending line but this time through rectifiers R5 and R6 and the contact aj belonging to chain 56.

Fig. 5 shows the feeding device of concentrator A: the alternating current is sent from set B over the two wires ta--tb in parallel Iand the two Wires ta-tb in parallel. It is received at transformer 61, connected to the wire pairs by condenser bridges 62-63. A complete rectifier 64 is supplied by transformer 61. Its positive pole is grounded and its negative pole supplies the battery side of the relays and magnets.

Referring to Fig. 6, the sending `device contained in set B comprises a synchronized-stepping chain, a device feeding alternate pulses of the stepping chain of set A over line ta-tb, a code-sending chain connected to the same wires tif-tb' as that of set A and a feeding bridge supplying these two chains in one direction or the other. With this sending device are assoicated the ringing device, with its separate battery, the option `device and a supervisory device for the connection.

An outgoing call operates relay dh over the front contact of one of the first four identification relays cb1-4, similar to relays (zb-1 4 of Fig. 4, and the back contact of a relay db-Z. The ringing loop (4th path) of set A is rthen supplied in series with the ringing loop (3rd path) of set B as follows: positive pole of separate battery 66, t-dh, wire tb', loop in set A, wire ta', r-db-2, rectifier R7, contact chain 67, t-dh, checking chain of `magnets r-SS-l-z6, r-SX-l-Z, lrelay da(I), negative pole of battery 66. lf the control devices of set A are in normal position, as they should be, the loop is closed and relay da operates and locks for the duration of the connection: ground, r-ci, r-dg, t-da, da(1l), battery.

Relay da operates, for supervisory purposes, a slowreleasing relay idf: ground, t-da, r-cj, df, battery. Relay df will release with a time lag upon the operation of relay ci and during this time lag relay da will remain locked by ground, t-df, etc.

For the option as to thecall to be handled, relay daI having operated for an outgoing call, with dh operated, operatesoutgoing-call relay alb-1 over ground, t-da, t-dh, r-db-Z, db-1, battery. Incoming-call relay db-Z is cut oit over a back contact of relay dh; the outgoing call will therefore be handled even if lan incoming call has developed between the operation of relays dh and dbl. Relay alb-1 holds relay dh over ground, t-db-l, dh, so that the sending of the code will not be wrong should the incoming call disappear during the sending.

Y The operationA of the relay prepares the supplying of the sending chain in the negative direction with the separate sending battery: positive pole of battery 68, t-a'b-, wire tb', loop in set A, wire la', r-db-Z, R7, chain 67, break at the en'd of this chain, which for the moment is connected to the third path, coding relay, return wire 69, rectiiier R8, t-1a'b-1, negative pole of battery 68.

Referring to Fig. 7, relay da starts the pulse-rate device. Slow-releasing relay dc-ll is operated over ground, t-da, tedbl, r-dc-2. Slow relay dcfZ is operated thereupon o'ver the same ground land t-dc-i. Relay dc-Z cuts off relay dc-l, which releases. Relay (lc-2 releases in turn and .the cycle recommences. Each complete cycle of relays ric-1 2 corresponds to one pulse, positive or negative.

When relayl dc1 operates the irst time, relay ddisi operated over ground, t-da, t-'dc-l, r-dd-Z, dd (1)-l, battery. When relay dc-Il'releases, relay dal-1 holds in series with dd-Z, which operates: ground, t-da, r-dc1, t-dd-1, MUD-, rid-2, battery. On the second energization of relay ric-ll, relay dal-2 holds without going through relay da-l, which releases: ground, t-da, edc-ll, t-dd2, fd2, battery. When relay ic-1 releases, relay tid-2 releases with it. Onthe third energization of relay dc-l, relay daf-1 operates again, and so forth.

Referring back to Fig. 6, between the operation of relays da and ad-l the stepping chain of set A (line ta-tb) is supplied in the negative direction, without any effect on this chain: positiveY pole of separate battery 70, r-dd-i, wire tb wire ta, t-da, r-dd-l, negative pole of batttery 76. Thus a negative pulse will be sent during each unoperated period of relay dri-ll. Positive pulses are sent during the operating periods of this relay: positive pole of battery 79, t-Itd-l, wire ta Wire tb, t-ddl, negative pole of battery 76).

The synchronized-stepping chain of set B -is like the one of set A: relays cf-l-i, ch-16 and cj, respectively corresponding to relays af, al1 and ai; the first path comprises contact chain 71 and the odd relays (and relay cj) to battery; the second path comprises contact chain 72 and the even relays to battery. However, the supplying of this chain and the locking of its relays are simplified. The switching between the two paths is effected directly by an inverter of relayV ld-l: ground, t-rda,l t-dd-l, chain 7l; same ground, r-ad-isl, chain 72.. The relays lock OD the same ground controlled by the front contact of relay da, the odd relays over chain 73 and the even relays over chain 74hV Y Upon the operation of relay ci on the eleventh pulse (positive pulse supplied' by the sixth energization of relay dal-1), relay dye-1(Fig. 7) holds over r-cj and holds relay ridoperated under the control of relay da (as also relay re-2)'. Relay cj (Fig. 6) holds: ground, t-da,.tdd 1,. #cla-6, ci.,;battery (its operating circuit); relays cha 5,. r6 rernainy locked` under the control of relay da.- Line4 iam-tb'` continues to be supplied in the positive direction, thus holding relay aj (Fig. 5) in set A.

. The code-sending chainis exactly like that of set A: coding relays cg-1-4 and ci-16; iirst path (for outgoing calls) over rectier R7, stepping-contact chain 67, identitication contacts t-cb-1-4 and t-cd-1-6, the coding relays, return wire 69 and rectifier R8; second path (for incoming calls) over rectifier R9, stepping-contact chain 75, the coding relays, the same return wire and rectiiier R10. The return wire is controlled by a front contact of relay idc-2 (t-dc-2) thus the pulses start in the sending chain some time after (the operating time of relay dc-Z) the pulses in the stepping chain and end some time before (the openating time of relay dc-l, Fig. 7), thereby ensuring' at each moment of the stepping the operation of onlyY the corresponding coding relay after the switching eiected by the corresponding stepping relay in the stepping chains of the two sets.

The third path (outgoing-call signal), at the end of the tirst, has already been described. The fourth path (incoming-call signal) is the same as the third in its operative portion: rectifier R9, chain 75 terminated by r-cf-l, r-dh, checking chain SS-l-Z and SX-12, da (il), battery 66, r-dh. The fth path (supervision), prepared by the operation of relay cj, comprises relay ck front contacts associated with magnets SS-1-26, in parallel, and front contacts associated with magnets SX-1-2, in parallel. Relay ck operates upon the operation of relay ci after the operation of a selecting bar and of the separating bar in the two sets and when a selecting magnet has been chosen in set A (operation of relay am, Fig. 9). It locks over a circuit prepared when a selector magnet has been seized but not yet operated: ground, Pda, t-jm-l-S, each in series with the back contact of the corresponding magnet r-V-l-f, t-ck, ck (II), battery.

Upon the operation of relay cj, relay df releases slowly, as already stated. Upon the operation of relay ek, relay dg operates over: ground, lt-da, t-ck, dg, battery, and locks over: ground, t-da, t-dg, dg, battery. Relay da holds over ground, zf-df, t-ck, t-da, da (II), battery. When relay ck releases after the connection (magnets V operated in both sets), relay da releases and causes the release of all the relays mentioned, as also of the selectl ing-bar magnets. It also breaks the stepping line and the code-sending line, thereby causing the release of supervision relay aj (Fig. 5 and of the other relays mentioned, as `also of the selecting-bar magnets in set A.

AHowever, if the connection operations are notY performed quickly after the operation of relay ci, relay df releases meantime and cuts oi relay da, which falls back and cancels the preceding operations in order to handle the same call again, or some other call, depending upon the circumstances.

Returning now to the case of an outgoing call, the option device has operated and the pulse-rate device has been started as stated above. On the rst pulse (positive, pulling up of relay dd-l), relay cf-l operates in set B at the same time as relay ttf-l in set A. The call-signal path is broken in both sets and the code-sending path is set up as follows: positive pole of battery 68, t-db-1, wire rb', second path in set A, wire ta', r-db-Z, tirst path in set B (rectifier R7, chain 67 Wire 69, rectifier R3), l-dbe-l, negative pole of battery 68. The current llows at the moments defined by the stepping (chain 67,

Fig; 6, and chain 56, Fig. 5) for which identication co'- tacts I-cb-1-4, t-cd-l-6 are closed, and the correspond-A ing selecting relays (cg, ci, ag, ai) are positioned simultaneously.

At the end ofthe stepping, relays cj and aj operate and 4by the operation of` a preparation relay 1m-1 8, the cor- 'i3 responding selector magnet V-l-S being in home position, in set A (Fig.

Where an incoming call is identified in set A while there is no outgoing call in set B and its relay dh is unoperated, relay da operates as follows: positive pole of battery 66, r-dh, Wire la (positive supply) third path in set A, closed by a relay arl-1 5 (Fig. 5), wire tb (Fig. 6), r-db-l, rectiiier R9, fourth path (incoming-call signal), comprising second-path chain 75, r-dh, chain r-SS-1-26 and r-SX-LZ, 161(1), negative pole of battery 66.

With relay dh unoperated, relay do operates option relay cib-2: ground, f-da, r-dlz, r-dh-ll, dln-2, battery. The operation of relay rib-2 ensures the handling of the incoming call by cutting oft relays dit and dln-l. The pulserate device is started as in the preceding case and causes the stepping chains in both sets to operate in synchronism. Relay lb-2 prepares the positive supplying of the codesending chains by connecting the positive pole of battery 68 to wire ta and the negative pole to return wire 69 through rectifier R10.

The following circuit is established upon the operation of the iirst stepping relay in both sets: positive pole of battery 6%, tdb-2, wire la (positive supply), rst path in set A, wire tb', r-db-l, rectifier R9, second path in set B, comprising stepping-contact chain 75, the selecting relays and return wire 69 with t-dc-Z, rectifier R10, t-db-Z, negative pole of battery 68. The selecting relays are positioned in both sets under the control of the identication relays of set A, nwhose front contacts are cornprised in the first path of this set, as described with reference to Fig. 5.

Alfter that positioning, relays cj and aj, ck, etc., operate as in the case of an outgoing call.

Fig. 6 shows also the equipment of set B intended to supply set A. The alternating current is supplied from a transformer 76, over condenser bridges 77 and 78, (l) to wires trl-tb in parallel and (2) to wires tri-tb in parallel.

Referring to Fig. 8, the trunkseizing device provided in set B operates immediately after relay da. In this device, each trunk has associated with it, besides the selector on the crossbar switch, with its magnet V-1-8, a seizing relay itz-1 8 and an auxiliary relay jm-l-S. Upon the operation of relay da, the relays ja of all free trunks, whose magnets V are in home position, are operated: ground, t-da, r-dj, r-V-l-S, ja(l)-ll5, battery. Over the chain of contacts of relays ja (chain Sib), the irst in order, namely, relay jaeN, locks: ground, t-da, dj, chain 80 up to t-ja-N, ja(Il)-N, battery, and breaks the chain beyond. Relay dj operates and breaks the operating circuit of relays ja, which release, except relay a-N, which has been locked. Over chain 81, similar to chain Si), the corresponding auxiliary relay is oper-ated: ground, Pda, z-dj, chain 81 up to t-ja-N, jm-N, battery. If all the trunks are busy but one of them is released in time during the code-sending operation, it is seized immediately.

Referring to Fig. 9, a seizing relay crm-1 8 is associated with each trunk in set A. Upon the operation of relay jm-N in set B, relay am-N operates over the a Wire of the trunk: (Fig. l0) battery, resistor, t-dj, t-jm-N, Wire a (Fig. 9) wire an r-V-N (a back contact associated with the magnet of the corresponding selector), am-N, ground. Relay arri-N holds independently of this latter contact over the a wire, t-amf-N, ram-N, ground.

`The seizing device then waits for the end of the code sending.

The selecting-bar magnets are operated in proportion as the code sending progresses and as the selecting relays are positioned. Referring to Fig. 9 and always assuming that line 17 (that is, line No. 4 in group 2) is a calling or a called line, dividing magnet SX-l is operated upon the operation of relay zg-1 over ground, r-SX-l, 2 in series, Mtg-1, SX-1, battery. It opens its associated back contact, which breaks the operating circuit just mentioned,

and holds on reduced current over ground, resistor, `Mtg-1.V Magnets SS-l-26 are controlled by two similar switchings, setup by contacts of selecting relays mld-6; the first, supplied by relay zg-3, controls magnets SS-1-13, `while the second, supplied by relay ugh-4, controls magnets 14-26. For line 17, it is relay zg-4 that is operated in the code sending. Forthwith, upon the operation of relays a-Z-S, magnet SS-17 is operated over ground, t-rzg-t, t-a1-2, t-ai-S, SS-17, battery. The operation of relay frm-N and of magnets SX-l and SS17 prepares the fifth path in set A (Fig. 5).

Referring to Fig. l0, in set B magnets SX-l-Z and SS-1-26 are controlled by switchings similar to those of set A but under the general control of relay da (over ground, t-da, etc.) and magnets SX do not reduce their holding current. The operation of magnets SX and SS prepares the fifth path (over relay ck, Fig. 6), and the operation of relay jm-N has already prepared the locking circuit of relay ck.

When the operation of the synchronized-stepping chains has ended and relays ai and ci are operated in sets A and B, the fth paths are switched in and relay ck (Fig. 6) opcrates as described above. Relay ck operates the previously-chosen selector: (Fig. l0) ground., t-ck, t-jm-N, V-N(I), battery. This magnet locks over an advanced make contact: ground, t-jmN, tx-V-N, V(II)N, through a fourth relay associated with the trunk, jn(I)-N, battery. Relay jn-N operates. At the same time, relay ck applies positive battery to the "b wire: positive battery, t-ck, t-jm-N, "b wire. In set A this battery operates the corresponding selector magnet: (Fig. 9) b wire, t-am-N, rectifier R11, V-N(I), t-am-N, t-am-N (doubling r-V-N), a Wire. The "a wire is at this moment connected to negative battery in set B, as stated above..

Set B therefore operates distant magnet V-N of set A under a voltage that is in principle doubleV the normal potential between battery and ground.

A third relay, jc-1-8 (Fig. 10), associated with each trunk in set B, is operated upon the seizure of trunk N in the case of :an incoming call: ground, t-db-Z, t-im-N, jc-N.

The energization of magnet V-N effects the connection inthe crossbar switch: trunk N is connected to line 17 on the exchange side. The test cut-olf relay cx-l52 associated with this line -is operated: ground, r-V-N, contacts "d, csc-17, battery. This cuts off the c wire of line 17, exchange side, from the test and identification devices.

The connection made by magnet VN places in the case of an incoming call a false subscriber loop on the "a and b wires towards the exchange: a wire, a contacts of lthe switch resistor, t-jc-N, -V-N, resistor, b contacts and wire. This loop causes the usual operation of the line circuit at the exchange, for example of relay lr (Fig. ll): ground, t-cor, a wire, Iabove-mentioned loop, b wire, r-cor, Ir, battery. Relay lr causes the call hunting. In the case of an outgoing call, the exchange a and "b Wires are extended lto set A upon the opera-tion of relay jb: ground, "c wire, c contact, jb, battery.

In set A (Fig. 9) magnet V-N connects trunk N to line 17, subscriber side. The test cut-off relay ax-1-52 associated with this line is operated in a locking circuit for magnet VnN: ground, r-an-N, teV-N, V(II)-N, rrc contacts, ax-l7, battery. Relay itx-17 cuts off line 17, whether calling or called, from its supply in set A and from the test and identification devices through which the a wire is supplied. Relays an-l-S are .releasing relays associated with the trunks in set A. Relay zn-N is connected to the a wire of the trunk by a front contact associated with magnet V-N: ground, tx-V-N, art-N, rectiiier R12, a Wire, but rectifier R12 prevents it from operating in parallel with relay am-N and magnet V(I)-N, which are already supplied by this wire.

The operation of magnet V-N in set A breaks the fifth path (Fig. 5), which loops line ta-tb in this set. It also breaks the operating circuit of relay ck(1) (Fig. 6) in- 15 serted in the fifth path set up in set B. The locking circuit of this relay, ck(II), is broken by the operation of magnet V-N in set B. Relay ck falls back and breaks the locking circuit of relay da(l'l), relay dg being operated.

The above operation, following the operation of relay cj at the end of the synchronized stepping, must be covered by the releasing Ilag of relay df, cut off by relay cj. Were these operations to take an unduly long time, because all the trunks were busy or because of any operating failure, relay df would release first and would cut off relay da.

Relay da upon cle-energizing releases the whole control equipment. It removes (Fig. 6) the operating and locking grounds ofthe stepping and coding relays in set B: relayscj and ch-`, 6 and cg-1, 4 and cz'-2, 3 (for line 17) release. It also cuts the supply of stepping line ta-tb, thereby causing the release of relay aj (Fig. 5) in set A. Relay aj upon releasing removes the locking ground from wire 57, thereby causing the release of stepping relay al1-6 and of coding relays ag-l, 4 and zi-2, 3 (for line 1.7). Relay da causes the release of relay dg (Fig. 6) 'and of the operated option relay, dbd. or db-Z, depending upon the case. It releases the pulse-rate device (relays lic-1 2 and dnl-1, Fig. 7) and the seizing device (relays jfl-N, dj and jm-N, Fig. 8). lt removes the operating ground of magnets SX `and SS (Fig. l0), while the selecting (or coding) relays of set A cut ofi, upon releasing, the correspondi'ng magnets in this set (Fig. 9).

Inet-he case of an incoming call, the release of relay jmN (Fig. l0) modifies the supply of the trunk to set A. The a wire is grounded: ground, resistor, ILV-N, r-jb-N, r-jm-N, a wire. The b Wire is connected to the battery through relay jc-N, whose operating ground is removed at this moment: "b Wire, r-'jm-N, r-jb-N, jc-N, battery. in set A (Fig. 9) relay am-N, short-circuited between two grounds, releases and is disconnected from the trunk. This latter is then extended to the subscriber: a wire of trunk N, r-ameN, n contacts of the switch, of wire to subscriber 17; same connection for the b wire. Relay jc (Fig. l0) holds over the calling subscribers loop while the exchange hunts for the cali under the action of the above-mentioned false loop. When the calling line is seized, the exchange applies a ground to the c WireV and relay jb-N operates: ground, c wire, exchange side, jb-N, batte-ry. The line is then fully connected a Wire exchange side, a contacts, t-jb-N, r-jm-N, a wire of the trunk (Fig. 9), above-mentioned connection to the subscriber-side a wire; same connection for the b wire. Relay ,ic-N is cut `off and falls back slowly. In the case of an outgoing call, relay jb operates immediately on the ground applied to the c wire of the outgoing call. Over its grounded front contacts (Fig. l0), relay ,ib-N holds the locking circuit of magnet V(II)-N.

At the end of the call, the exchange removes the ground from the c wire. Relay jb releases and causes the -release `of magnet V, which causes the release of relay cx. Relay in holds over its second winding through releasingrelay an or set A: positive battery (Fig. l0), jn(ll)-N, r-V-N, r-jb-N, r-jm-N, a wire of the trunk (Fig. 9), rectifier Riz, air-N, lx-V-N, ground. Relay an operates and breaks the locking circuit of magnet V(II)N. This magnet releases together with the relay ax included in itsl locking circuit. Upon releasing, it breaks the circuit of relay an, which releases together with the relay jn included in this latter circuit. The trunk is thus released, and the lines, both on the subscriber and on the exchange side, are connected to the test and identification devices.

A description will now be given of a variant (Figs. 1'2-16) of Fig. 2 wherein the selection of the magnets of the crossbar switches is controlled by the identification relays. inthe embodiment shown it will be assumed that the concentrators carry l2 x 4:48 lines, so as to use l2-element rectifier matrices.

Fig.` l2' shows'the same general layout described with reference to Fig. 4 for call testing and identification. The relationship tables given above are here as follows;

In this arrangement, matrix B is a 4-element matrix, like matrix A. It will be assumed that the calling line is No. 16, that is, line No. 4 in group 2. This line will be identified by relays aa-2 and ali-2 in matrix A, relays ac2 and ald-2 in matrix B and relays ae-S and :1d-3 in matrix C.

For the operation of the identification relays as selec-Y tion relays positioned in accordance with a call present in the other set, the operating grounds of the matrices are controlled by back contacts of a relay ak, operating taps 81-484 and 91-96 are provided on the (vertical) wires of the identification relays and decoupling rectifiers are included in these wires between these taps and the common operating ground. It will be recalled that in concentrator B, where the test potential is the ground on the c wire, the matrices will be supplied by batteries, i n practice with resistors in series, and the various rectifers will ybe inverted.

Fig. 13 shows the same general layout of the stepping yand code-ending chains as described with reference to Figs. 5. The stepping chain is similar to that of Fig. 5 but with a relay ak added at the end of the contact chain 53 (negative path) operating the even relays. In the case of `an incoming call, the first stepping pulse'is positive, as in the case of Fig. 5; relay af-l operates and switches chain 53 to relay a'f-Z, which is operated bythe second pulse, a negative pulse. Relay ak does not operate, and the general operation is as has been described above. In the case of Van outgoing call, the first pulse will be negative and will operate relay ak, after which the next pulses, positive and negative, will cause the chain to operate as in the preceding case.

The sending chain comprises no relays, because it positions the identification relays of Fig. l2 (ab-1-4 and zd-1 6). However, the general arrangement of its paths is the same, and its auxihary paths, namely, the third (incoming-call signal), the fourth (normally closed loop offered to the outgoing-call signal) and the fifth (suprvision of the connection) are similar.

In the first path, contact chain 54 is looped directly to return wire 55 under the control of identification contacts for incoming calls. The second path, which must position the identification relays in the case of an outgoing call, closes at the beginning of chain 56 on a pulsing relay ap after the operation of relay ak in the stepping chain. The rest of the chain is then supplied, at moments determined by set B, by the ground pulses repeated by relay ap, which is cut off at the same time from the rest of return wire 55 (the ground contact, f-ap over the rest of chain S6 and contact r-ap in wire 55). Chain 56 directs these pulses to wires Sil-84 and 91-96 in order to operate the corresponding identification relays.

The operation of the device of Fig. 13 in the case of an outgoing call is as follows. The call `signal fiows over the fourth-path loop: wire tb', rectifier R5, contact chain 56, contact chains r-SS-1-24 and r-SX-1-2, wire 55 bis, r-ap, wire 55, rectifier R6, wire ta. The sendingchain is supp-lied in this direction (negative). Set B thereupon sends the stepping pulses. The first stepping pulse properly so called (positive) is preceded in this case by arneg-v 

